The invention concerns a method for the electrochemical deposition of hydroxyapatite layers onto metal and ceramic surfaces, the actual electrochemical coating being combined with a pre-coating of the substrates by sol-gel processes, using a calcium and (hydrogen) phosphate-containing electrolyte by means of pulsed direct current. Materials coated in this way are used in the form of biocompatible implants in human and veterinary medicine and are distinguished by particularly high grow-in rates. In contrast to conventional methods of generating hydroxyapatite layers (conventional or microwave sintering of hydroxyapatite produced by the wet-chemical method, deposition by other electrochemical, plasma or laser-aided methods or by sol-gel techniques), this method is distinguished by the application of uniform hydroxyapatite coatings which adhere well and have a small amorphous portion and an optimum layer thickness (5-25 μm) whilst requiring comparatively low expenditure in terms of apparatus, energy, time and material.
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1. A method for electrodepositing hydroxyapatite layers comprising pre-coating a surface of a substrate with a sol-gel having elements of the chemical composition of the surface and/or the hydroxyapatite layer by subjecting the surface to sol-gel coating at least once, and electrochemically depositing hydroxyapatite on the sol-gel coating.
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This is a national stage application of PCT EP95/03499, filed on Sep. 6, 1995.
The invention relates to a method for electrodepositing hydroxyapatite layers of the general composition Cax+9 (PO4)x+5 (HPO4)1-x (OH)x+1, in which x represents a value between zero and 1, on metal surfaces and ceramic surfaces. Materials, coated in this manner, are used in the form of biocompatible implants in human and veterinary medicine, which are distinguished by particularly high growing-in rates. Various methods have already been described for producing hydroxyapatite and other calcium phosphate coatings. However, all of them are afflicted with certain deficiencies.
The already established methods include plasma spraying of hydroxyapatite1. Although this method is comparatively expensive, it has not been possible, because of the line-by-line or the side-by-side application, to produce coatings, which are uniform in relation to the thickness, adhesion and homogeneity of the layer if substrate geometries are somewhat complicated. Hydroxyapatite coatings with consistently lower adhesion can be prepared by drying2, conventional sintering3 or microwave-sintering4 of hydroxyapatite, produced by methods involving wet chemistry or deposited from suspensions. Expensive (vacuum) sintering processes for producing uniform coatings are also characteristic of the sol-gel5 and the electrophoresis6 methods. On the other hand, a high technical effort for the actual coating process characterizes methods, which are based on the sputtering technique7 and the pulsed laser deposition process8. An electrochemical method9, which is suitable for coating mechanically pretreated surfaces of titanium (alloy) substrates with calcium phosphate, can be realized more easily technologically. A more uniform layer growth is said to be achieved by using pulsed direct current10,11 (20 sec on-off cycle; direct current as in the original method. However, the adhesion of the calcium phosphate layer to the titanium substrate is not increased significantly by these means.
It is an object of the present invention to develop a method for depositing hydroxyapatite on metal, alloy and ceramic surfaces, which is distinguished by a uniform, well adhering coating of optimum thickness and by a low proportion of amorphous materials, while the expenditure for equipment, energy, time and material is relatively small.
Pursuant to the invention, this objective is accomplished owing to the fact that the actual electrochemical coating process, using an electrolyte containing calcium phosphate and calcium hydrogen phosphate and a pulsed direct current of suitable frequency, is preceded by a preliminary coating process using a sol-gel technique. The sol-gel couting is a mutual approximation of the chemical composition of the substrate and of the hydroxyapatite layer because the solution used for the sol-gel coating has elements of the chemical composition of the substrate and/or the hydroxyapatite layer. As a result of the solution used for the sol-gel coating including elements of the substrate and/or the hydroxyapatite coating layer, there is a significant increase in the adhesion of the hydroapatite coating layer. The increase in adhesion is achieved by the number as well as the type of solutions used. With respect to the areas of application of the invention, the substrates themselves, which are to be coated, should have sufficient biocompatibility. This concerns, in the case of the metals, for example, titanium and platinum, in the case of alloys, various iron and nonferrous metal alloys, particularly high-grade steels, CoCr28Mo and TiA16V4, and, in the case of ceramic materials, predominantly oxides, nitrides, oxynitrides and carbonitrides, which contain, in their composition, one or more metals from the and groups 4 and 5 of the periodic system of the chemical elements. The substrates to be coated consist either completely or partly of the materials given above or these materials, in the form of monolayer or multilayer coatings on basic objects of metal, alloys, ceramics, glasses or plastics, are a component of the substrates. The substrates are pretreated by a sol-gel coating using alkoxides, which contain an element of groups 3-5 and 13-15 of the periodic system of the chemical elements, or mixtures of such alkoxides, which optionally contain calcium phosphate ions and/or calcium hydrogen phosphate ions or esters of phosphoric acid as further components, by means of one or several applications by spraying, ultrasonic fogging or by the dip coating method. It is also possible to carry out the preliminary treatment by a sequence of (electro)chemical passivation and sol-gel coating.
The pretreated substrates are coated electrochemically in an electrolysis cell, which is equipped with the usual equipment for tempering and for mixing the electrolytes, the calcium phosphate ions and the calcium hydrogen phosphate ions in a molar ratio of approximately 1.5 to 1.7, an inert anode, for example of carbon, gold or platinum, and the substrate itself as substrate, using a pulsed direct current with a pulse frequency between 1 and 300 Hz and preferably of 50 Hz with identical on-off intervals, and a voltage of 2 to 10 V. Optimum temperatures for the quality of the coating fall within the range of 20° to 40° C. The coatings, so prepared, are usually washed with deionized water and dried in a stream of air, which optionally is pre-heated. Furthermore, tempering of the coated substrates at temperature between 300° and 500°C is possible but not absolutely essential. If such a thermal treatment is carried out, it is associated with the useful effect that the coating contains carbonates proportionally.
The coatings, prepared pursuant to the invention, can be sterilized by conventional methods.
The thickness of the hydroxyapaptite deposition can be varied by varying the electrolyte concentration and the remaining pretreatment and process parameters and, for typical applications, is of the order of 5 to 25 μm. With that, a covering density of 1 to 3 mg/cm2 is achieved.
The advantage of the invention lies therein that, by the method above, hydroxyapatite can be deposited on metal and ceramic surfaces of the type, required for use as biocompatible implants in human and veterinary medicine. Moreover, the application of uniform, well adhering hydroxyapatite layers, containing a small proportion of amorphous materials and having a thickness optimum proportions, is assured by a sol-gel pretreatment.
The invention is described in greater detail in the following by means of examples, which are given by way of illustration and not by way of limitation.
A titanium panel, having the dimensions of 80×10×1.5 mm, is cleaned in an ultrasonic bath with a 1:1 mixture of isopropanol and acetone. Using the dip coating technique (withdrawing rate of 1 cm/min), the surface is subjected twice to a sol-gel coating procedure, using a solution consisting of 0.05 moles/L of Ti(i-C3 H7 O)4, 0.05 moles/L of Si(OC2 H5)4 and 0.1 moles/L of HCI in the form of 37% hydrochloric acid for the first treatment and 0. 05 moles/L of phosphoric acid in the form of 85% phosphoric acid for the second treatment in isopropanol. About 6 hours later, the hydroxyapatite is deposited electrochemically in a glass cell having a capacity of 100 mL using the pre-coated titanium panel as the cathode and using a carbon anode. A solution consisting of 0.1 moles/L of NH4 H2 PO4 and 0.167 moles/L of CaCl2, which is stirred magnetically at 22°C, is used as electrolyte. When pulsed 200 Hz direct current (equal on and off times) and a potential of 6 V are applied, a hydroxyapatite layer is deposited on the titanium panel within 10 minutes. Subsequently, the coated panel is washed twice with deionized water and dried for about 5 minutes in a current of warm air. A coating with a covering density of 2.16 mg/cm2 is produced on the electrode surface by this method.
As in Example 1, a titanium panel is passivated anodically in 5% phosphoric acid using a current density of 10 mA/cm2 and a potential of about 12 V and subjected to a sol-gel coating procedure by a spraying process using, a solution consisting of 0.05 moles/L of Ti(i-C3 H7 O)4, 0.04 moles/L of Si(OC2 H5)4, 0.01 moles/L of triethyl phosphate and 0.1 moles/L of hydrochloric acid in the form of 37% hydrochloric acid in isopropanol. The hydroxyapatite is deposited as in Example 1 using an electrolyte consisting of 0.1 moles/L Ca(NO3)2 and 0.06 moles/L Na2 HPO4.
As in Example 1, a titanium panel is subjected twice to a sol-gel treatment by the dip coating technique (withdrawal rate of 1cm/min) using a solution consisting of 0.05 moles/L of Ti(i-C3 H7 O)4, 0.05 moles/L of Si(OC2 H5)4, and 0.1 moles/L of hydrochloric acid in the form of a solution of 37% hydrochloric acid in isopropanol. After about 6 hours, hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 40°C
A titanium panel is treated as in Example 3. In addition, there is a further dip coating procedure in a solution consisting of 0.025 moles/L of Ti(i-C3 H7 O)4, 0.025 moles/L of Si(OC2 H5)4, and 0.05 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in isopropanol and 0.05 moles/L of CaCl2.2H2 O in ethanol. After about 4 hours, hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 180 Hz.
As in Example 1, a titanium panel is subjected twice to a sol-gel treatment by the dip coating technique (withdrawal rate of 1 cm/min) using, a solution consisting of 0.033 moles/L of Ti(i-C3 H7 O)4, 0.033 moles/L of Si(OC2 H5)4, 0.033 moles/L of Al(i-C4 H9 O)3 and 0.1 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in isopropanol. In addition, there is a further dip coating procedure using a solution consisting of 0.0167 moles/L of Ti(i-C3 H7 O)4, 0.0167 moles/L of Si(OC2 H5)4, 0.0167 moles/L of Al(i-C4 H9 O)3 and 0.1 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in isopropanol and 0.05 moles/L of CaCl2.2H2 O in ethanol. After about 4 hours, hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz and 3.8 V. During 7 minutes, a coating density of 1.98 mg/cm2 is attained.
A glass plate, having the dimensions of 80×20×1 mm and coated with 2 μm of titanium, is pretreated as in Example 5 and coated with hydroxyapatite. A scanning electron microscope photograph (5 kV) of a fractured edge preparation shows that the average height of the coating is 15 μm.
A glass plate, coated with 2.5 μm of TiN, is treated as in Example 6. A scanning electron microscope photograph (5 kV) of a fractured edge preparation shows that the average height of the coating is 10 μm.
A high-grade steel panel, having the dimensions of 80×20×1 mm and coated with 2 μm of TiN, is subjected to a sol-gel treatment by the dip coating technique (withdrawal rate of 1 cm/min) using a solution consisting of 0.033 moles/L of Ti(i-C3 H7 O)4, 0.033 moles/L of Si(OC2 H5)4, 0.033 moles/L of Al(i-C4 H9 O)3 and 0.1 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in isopropanol. In addition, there is a further dip coating procedure using a solution consisting of 0.0167 moles/L of Ti(i-C3 H7 O)4, 0.0167 moles/L of Si(OC2 H5)4, 0.016 moles/L of Al(i-C4 H9 O)3 and 0.1 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in isopropanol and 0.05 moles/L of CaCl2.2H2 O in ethanol. After about 4 hours, hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz and 3.5 V. During, 5 minutes, a coating density of 1.46 mg/cm2 is attained.
A high-grade steel panel, having the dimensions of 80×20×1 mm and coated with 2 μm of TiN, is subjected to a sol-gel treatment by the dip coating technique (withdrawal rate of 1 cm/min) using a solution consisting of 0.05 moles/L of Ti(i-C3 H7 O)4, 0.05 moles/L of Si(OC2 H5)4 and 0.1 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in isopropanol. In addition, there is a further dip coating procedure using a solution consisting of 0.025 moles/L of Ti(i-C3 H7 O)4, 0.025 moles/L of Si(OC2 H5)4 and 0.05 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in isopropanol and 0.05 moles/L of CaCl2.2H2 O in ethanol. After about 4 hours, hydroxyapatite is deposited electro-chemically under the conditions of Example 1, but at 50 Hz, 4 V and 35°C
A high-grade steel panel, coated with 2.2 μm of TiN, is pretreated as in Example 8. After about 4 hours, the hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz, 3.8 V and 25°C During 8 minutes, a covering density of 1.58 mg/cm2 is achieved. A mechanically abraded coating sample is dried for 2 hours at 200°C, dissolved in concentrated hydrochloric acid and analyzed spectrophotometrically (Ca2- : arsenic(III) azo method, PO43- : molybdenum blue method), the calcium to phosphorus ratio is 1.58.
A polytetrafluoroethylene panel, having the dimensions of 70×20×5 mm and coated with 1.8 μm of TiN, is pretreated as in Example 9. After 4 hours, the hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz, 40 V and 25°C During 7 minutes, a covering, density of 1.28 mg/cm2 is achieved.
A high-grade steel panel, coated with 2.4 μm of titanium niobium oxynitride, is pretreated as in Example 9. After 4 hours, the hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz, 3.5 V and 25°C During 5 minutes, a covering density of 1.32 mg/cm2 is achieved.
A high-grade steel panel, having the dimensions of 80×20×1 mm and coated with 2 μm of titanium zirconium nitride, is subjected to a sol-gel coating by the dip coating technique (withdrawal rate of 1 cm/min) using a solution consisting of 0.05 moles/L of Ti(i-C3 H7 O)4, 0.05 moles/L of Zr(OC4 H9)4 and 0.1 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in n-butanol. In addition, there is a further dip coating procedure using a solution consisting of 0.025 moles/L of Ti(i-C3 H7 O)4, 0.025 moles/L of Zr(OC4 H9)4 and 0.05 moles/L of hydrochloric acid in the form of a 37% solution of hydrochloric acid in n-butanol and 0.05 moles/L of CaCl2.2H2 O in ethanol. After about 4 hours, hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz, 4 V and 25°C
A TiAl6V4 disk (14 mm in diameter and 1 mm thick) is subjected to a sol-gel coating procedure by means of ultrasonic fogging (800 kHz, 200 W, nitrogen carrier gas) using the solutions given in Example 8. After 6 hours, hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz, 4 V, 25°C and with sheet platinum as anode and a platinum wire as the cathode holder.
A TiAl6V4 disk (14 mm in diameter and 1 mm thick), coated with 2 μm of TiN, is subjected to a sol-gel coating procedure by means of ultrasonic fogging, (800 kHz, 200 W, nitrogen carrier gas) using the solutions named in Example 9. After 6 hours, hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz, 3.5 V, 25°C and with a high-grade steel clamp as the cathode holder.
A high-grade steel panel (1.4301), having the dimensions of 80×20×1 mm, is pretreated as in Example 9. After 4 hours, hydroxyapatite is deposited electrochemically under the conditions of Example 1, but at 50 Hz, 4 V, 25°C and with a high-grade steel chamber as the cathode holder. A covering density of 0.88 mg/cm2 is achieved within 3 minutes.
The coating preparations, produced in Examples 1 to 16, are tempered for 1 hour at 380°C under atmospheric conditions. At the same time, there is a loss in weight of the order of 10%. The coatings, so treated, contain carbon as shown by the IR spectra of coating material removed mechanically (ν∞at 1450 cm-1).
1. Radin, S. R. et al.: J. Mater. Sci. Mater in Medicine 1992, 33
2. Ducheyne, P. et al.: J. Biomed. Mater. Res. 1980, 225
3. Arita, I. H. et al.: Mater. Res. Symp. V (San Francisco, Calif.) 1993, Abstr. V2.2
4. Agrawal, D. K. et al.: Mat. Res. Soc. Symp. Proc. Vol. 269, 231 (1992)
5. Brendel, T. et al.: J. Mater. Sci. Mater in Medicine 1992, 175
6. Ducheyne, P. et al.: Biomaterials 1990, 244
7. Lacefield, W. R.: Ann. New York Acad. Sci. 1988, 72
8. Cotell, C. M. et al.: J. Appl. Biomater. 1992, 87
9. WO 92/13984
10. Shirkhanzadeh, M.: J. Mater. Sci. Letters 1993, 16
11. JP 05285212
Teller, Joachim, Neumann, H. Georg
| Patent | Priority | Assignee | Title |
| 10182887, | Mar 29 2010 | Biomet 3i, LLC | Titanium nano-scale etching on an implant surface |
| 10369253, | Oct 31 2011 | The University of Toledo | Method for modifying surfaces for better osseointegration |
| 10765494, | Mar 29 2010 | Biomet 3i, LLC | Titanium nano-scale etching on an implant surface |
| 6045683, | Dec 01 1997 | ALABAMA IN HUNTSVILLE, UNIVERSITY OF | Modified brushite surface coating, process therefor, and low temperature conversion to hydroxyapatite |
| 6139585, | Mar 11 1998 | DEPUY PRODUCTS INC ; DEPUY PRODUCTS, INC | Bioactive ceramic coating and method |
| 6168868, | May 11 1999 | PPG Industries Ohio, Inc.; PPG Industries Ohio, Inc | Process for applying a lead-free coating to untreated metal substrates via electrodeposition |
| 6569489, | Mar 11 1998 | DEPUY PRODUCTS INC ; DEPUY PRODUCTS, INC | Bioactive ceramic coating and method |
| 6736849, | Mar 11 1998 | DEPUY PRODUCTS, INC | Surface-mineralized spinal implants |
| 6974532, | May 01 2003 | New York University | Method for producing adherent coatings of calcium phosphate phases on titanium and titanium alloy substrates by electrochemical deposition |
| 7029566, | Sep 12 2003 | CPC CORPORATION, TAIWAN | Process of forming HA/ZrO2 complex coating on Co—Cr—Mo alloy |
| 7067169, | Jun 04 2003 | Chemat Technology Inc. | Coated implants and methods of coating |
| 7771774, | Nov 14 2005 | Biomet 3i, LLC | Deposition of discrete nanoparticles on an implant surface |
| 8309162, | Jan 28 2008 | Biomet 3i, LLC | Implant surface with increased hydrophilicity |
| 8486483, | Nov 14 2005 | Biomet 3i, LLC | Deposition of discrete nanoparticles on an implant surface |
| 8574615, | Mar 24 2006 | Boston Scientific Scimed, Inc. | Medical devices having nanoporous coatings for controlled therapeutic agent delivery |
| 8641418, | Mar 29 2010 | Biomet 3i, LLC | Titanium nano-scale etching on an implant surface |
| 8852672, | Jan 28 2008 | Biomet 3i, LLC | Implant surface with increased hydrophilicity |
| 8895098, | Dec 23 2010 | Heraeus Medical GmbH | Coating method and coating device |
| 8900292, | Aug 03 2007 | Boston Scientific Scimed, Inc | Coating for medical device having increased surface area |
| 9028907, | Jun 29 2010 | Heraeus Medical GmbH | Method and device for coating of a medical implant |
| 9034201, | Mar 29 2010 | Biomet 3i, LLC | Titanium nano-scale etching on an implant surface |
| 9131995, | Mar 20 2012 | Biomet 3i, LLC | Surface treatment for an implant surface |
| 9198742, | Jan 28 2008 | Biomet 3i, LLC | Implant surface with increased hydrophilicity |
| 9283056, | Mar 29 2010 | Biomet 3i, LLC | Titanium nano-scale etching on an implant surface |
| 9592319, | Jun 29 2010 | Heraeus Medical GmbH | Method and device for coating of a medical implant |
| 9757212, | Mar 29 2010 | Biomet 3i, LLC | Titanium nano-scale etching on an implant surface |
| 9763751, | Nov 14 2005 | Biomet 3i, LLC | Deposition of discrete nanoparticles on an implant surface |
| 9878346, | Dec 23 2010 | Heraeus Medical GmbH | Device for coating regions of a medical implant |
| RE36573, | Sep 26 1997 | Datec Coating Corporation | Method for producing thick ceramic films by a sol gel coating process |
| Patent | Priority | Assignee | Title |
| 5211833, | Jul 24 1991 | SHIRKHANZADEH, MORTEZA | Method for coating implants and surgical devices made of titanium and titanium alloys |
| 5310464, | Jan 04 1991 | Biomet Manufacturing Corp | Electrocrystallization of strongly adherent brushite coatings on prosthetic alloys |
| 5470668, | Mar 31 1994 | Los Alamos National Security, LLC | Metal oxide films on metal |
| 5643447, | Apr 06 1993 | Yissum Research Developement Company Of The Hebrew University Of | Thin layer chromatographic plates |
| CA2073781, | |||
| WO9321969, |
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